Figure 2. Two spatially separated memory sequences show no interference during training and both are strengthened by subsequent sleep.

(A) Network activity during periods of testing (T), training of two spatially separated memory sequences (S1/S2), and sleep (N3). Cortical PY neurons are shown. Color indicates voltage of neurons at a given time. (B) Left panels show an example of training sequence 1 (S1, top) and sequence 2 (S2, bottom). Middle panels show examples of testing both sequences prior to sleep. Right panels show examples of testing after sleep. Note, after sleep, both sequences show better completion. (C) Performance of S1 and S2 completion before any training (baseline), after S1 training, after S2 training, and after sleep (red). (D) Synaptic weight matrices show changes of synaptic weights in the regions trained for S1 and S2. Left panel shows weights after training S1; middle panel shows weights after training S2; right panel shows weights after sleep. Color indicates strength of AMPA synaptic connections. (E) Distributions of the net sum of synaptic weights each neuron receives from all the neurons belonging to its left neighboring group (S1 direction) vs its right neighboring group (opposite direction, defined as S1* direction below) within a trained region at baseline (left), after S1 training (middle) and after sleep (right). (F) Synaptic weight-based directionality index before/after training (gray bars) and after sleep (red bar).

Figure 2—figure supplement 1. Sleep replay improves performance for complex non-linear sequences.

(A) Example of the training protocol used for training a long non-linear sequence - BACEDFHGIJ. (B) Average group activations during baseline testing (left), after sequence training (middle), and after sleep (right). Top panels show average group firing rates during testing periods. Letters above each line indicate the group in the sequence. Sleep results in increase of the firing rates (higher peaks) and sharpening of the response times (narrower distribution) as compared to "before sleep". Bottom panels show normalized average group responses during testing periods. Sleep leads to an improvement and tuning of the responses such that testing after sleep results in the correct ordering of group activations and faster completion of the sequence. (C) Synaptic weight matrices in the trained region of the network before (left) and after (right) sleep. Color indicates synaptic strength. (D) Performance of the sequence completion at baseline, after training, and after sleep (red).